cooling problem, brake problem

So my coolant problem has been going on for a couple of week now, on and off. I brought the car to my local volvo tech and he couldn't replicate the problem (of course)

The problem is like this: I will start the car, and it will take about 20 minutes (while driving) to warm up to a normal temp (halfway on the temp gauge). This is because the cooling fan will not turn off. Once it reaches its normal temperature, the gauge will drop down, as if the car is cold (which it isn't, because the heat is still working). then the gauge will fluctuate from low to medium, and eventually just stay low (which causes the car to idle high and stay in 2nd gear longer). When i shut the car off, the cooling fan will stay on for about 5 minutes

now for the brake problem - just started yesterday

under normal acceleration (2-3k rpms) the brake failure light will come on ((!)) and it will stay on for about 30 seconds, then shut off. the brakes don't feel normal now. the pedal feel is different, like the power brakes aren't working as hard, but are still working a little.

So my coolant problem has been going on for a couple of week now, on and off. I brought the car to my local volvo tech and he couldn't replicate the problem (of course)

The problem is like this: I will start the car, and it will take about 20 minutes (while driving) to warm up to a normal temp (halfway on the temp gauge). This is because the cooling fan will not turn off. Once it reaches its normal temperature, the gauge will drop down, as if the car is cold (which it isn't, because the heat is still working). then the gauge will fluctuate from low to medium, and eventually just stay low (which causes the car to idle high and stay in 2nd gear longer). When i shut the car off, the cooling fan will stay on for about 5 minutes

now for the brake problem - just started yesterday

under normal acceleration (2-3k rpms) the brake failure light will come on ((!)) and it will stay on for about 30 seconds, then shut off. the brakes don't feel normal now. the pedal feel is different, like the power brakes aren't working as hard, but are still working a little.

HELP PLEASE! I'll post a video as soon as i can

Just a thought as I'm certainly no expert on repairs...but, maybe the coolant temp sensor is wacky. If you're getting heat and the gauge shows it's cold...then clearly the fluid is warm. I would imagine the ECU gets a signal from either that sensor or your gauge for the cold start idle. I'm sure there's a way to test the sensor to be sure it's functioning properly.

As for the brakes...sounds like the brake booster isn't operating fully. If you have a *hard* pedal...the booster isn't boosting. The question becomes...why? Could simply need a new booster. Or, there could be something restricting the booster from operating properly. Not sure if these Volvo's pull air from the intake manifold for the brake booster. If so, maybe you've got an issue with blockage. Maybe there's a valve between the intake and booster that's clogged????

Take all of this with a grain of salt. I'm such a fish out of water with these cars. BMW's...I'm a little better versed

Has your ABS been acting funny? Has the car been difficult to stop at times? Normal pedal feel but brakes not functioning? These are some things that my sister has experienced with her (now my) '98 S70 non turbo.

I wish I knew enough to truly help you. Hopefully, some of the experienced experts will chime in on what might be giving you issues.

As far as I know, the coolant temp sensor sends the temp readout to the gauge and to the ecu. The ecu then interprets and decides to turn the fan on by sending power to the relay. It sounds to me like that temp sensor is having intermittent issues. If you start the car and the fan comes on right away, you can try tapping the relay with a screwdriver, if it goes off the relay is bad. That wouldn't explain the temp gauge strangeness.
As far as the brakes go I'm not sure what to tell you, how does the fluid look? is it clean and full? Are there any codes logged, or does it just come on and go off?

Last edited by Paulie; 01-18-2010 at 09:10 PM.
Reason: to complete a thought

Your not crazy. That's weird... Could it be a wheel speed sensor? Maybe bleed the brakes down and get some clean fluid in there and take those sensors off and clean them. I don't know for sure, that's just a suggestion.

the brake issue is being fixed - it was a blown rear caliper (thats why it felt like i have to rear brakes). so that takes care of that.

as for the cooling issue, when i get the car back, i am going to try cleaning the water temperature sensor. the coolant was pretty dirty when i changed it, so maybe the sensor is dirty? if not i'll order a new sensor, they're only like $30